Mixing circuit



p 1952 J. M. 1.. JANSSEN 2,611,093

MIXING CIRCUIT Filed Feb. 14, 1947 J. M. L. JANSSEN \NVENTOR AGE NTPatented Sept. 16, 1952 2,611,093 Y MIXING, CIRCUIT Johannes MarinusLodevicus Janssen, 'Eindhoven, Netherlands, assignor to HartfordNational :Bank and Trust Company, Hartford, Conn, as

trustee Application February 14, 1947, Serial No. 728,711 In theNetherlands September 2, 19.4.4

Claims. (01. 2511-36) 1 This invention relates to a mixing circuitcomprising adischarge tube which contains at least a cathode, a controlgrid, 'a screen grid and an output electrode and whose control grid issupplied with one of the signals to be mixed.

According to the invention, the other signal, which is constitutedbyperiodical short pulses, is fed to the output electrode which has such abias voltage that it has only current passing through it during theoccurrence of the pulses, the desired beat frequency being obtained fromthe circuit of the output electrode.

The .circuitaccording to the invention has the advantage'of making itpossible to obtain output voltages whose frequency equals the sum or thedifference of the frequency fed to the control grid and of any harmonicof the pulse frequency fed to the output electrode, the conversionmutual conductance being very high and practically independent of theorder of the harmonic chosen. Thus, for example, the use of the circuitaccording to the invention even makes it'possible to derive aconsiderable output voltage whose frequency equals the difference of thefrequency supplied to the control grid and of the hundredth harmonic ofthe pulse frequency.

The circuit according to the invention can therefore be used withadvantage for the development of a large Zoneof accurately adjustablefrequencies ranging for example between zero and 20 M cycles/sec. Inaddition, as an alternative the circuit-according to the invention canbe used for frequency measurements, the measurement being undertaken bythe ascertainment of the difference frequency between the frequency tobe measured and themost proximate harmonic of a well known frequency.

In order that the invention may be clearly understood and readilycarried into effect, it will now'be described more fully with referenceto the accompanying drawing, in which two embodiments'are shown, Fig. 1being the schematic diagram of a first preferred embodiment of theinvention and Fig. Zbeihg the schematic diagram of the secondembodiment.

Referring to Fig. 1, .a discharge tube 1 comprises a cathode 2, acontrol grid 3,a screen grid 4 having a positive bias applied thereto, asuppressor grid 5 connected to the cathode and a plate-like outputelectrode 6. The control grid 3 and the cathode 2 have arranged betweenthem a source of voltage 1 which supplies one of the two signals to bemixed. The other signal, which is constituted by periodical shortpulses, is supplied by a source of voltage 8 arranged between the outputelectrode 6 and the cathode 2. An output voltage of the desired beatfrequency is obtained from an oscillatory .circuit 9 tuned to thisfrequency and also included in the circuit of the output electrode.

By means of a source of direct-voltage in the output electrode '6 issupplied with a low negative bias voltage .in such manner that thiselectrode has only current passing through itduring the occurrence ofthe pulses supplied by the source of voltage 8. It is now found that ifthe circuit 9 is correctly tuned, said circuit being for this purposepreferably tunable throughout a large zone, an output voltage can besecured whose frequency equals "the sum or the difference of thefrequency of the source I and of any harmonic of the pulse frequencysupplied by the source 8.

The frequency of the source I is preferably made variable throughout aband whose width is at least equal to halfthe fundamental frequency ofthe source 8 so that the constant use of a higher harmonic of the source8 for mixin permits of a continuous band of frequencies known with greataccuracy being obtained.

taking frequency measurements, the frequencies to be measured beingsupplied to the control grid 3 and the circuit of the output electrode sincluding in addition to a source of voltageB a low pass Ifilter whichis constituted by an inductance H and a condenser [:2 and whichis.shuntedby a leak resistance l3 so far as direct currents are concerned.The limit frequency of this filter is approximately equal to half the.fundamental frequency of the source.8, so that at the output terminalsi4 and IE only the difference frequency between the frequency to bemeasured .and the most proximate harmonic of the pulse frequencysupplied by the sourcea occurs. This difference frequency can bemeasured accurately by means of a calibrated low frequency oscillator.By a coarse frequency measurement, the harmonic of the source 8 which isto be added to the difierence frequency measured for obtaining thefrequency to be measured is then ascertained.

WhatI claim is: V

l. A circuit-arrangement-forproducing an output voltage, whose value isa function of the frequency relation existing between an oscillatorywave and one component in the harmonic spectrum of periodic voltageimpulses, comprising an electron discharge tube provided with a cathode,a grid and an anode, a grid-cathode circuit for said tube, ananode-cathode circuit for said tube, an impedance network connected inthe anode cathode circuit of said tube, means to apply an oscillatorywave to the grid-cathode circuit of said tube, and means to applyperiodic voltage impulses to said anode-cathode circuit to render saidtube conductive solely during the occurrence of said impulses, saidimpulses having a duration which is short with respect to the intervalbetween successive impulses, said network having a frequency responsecharacteristic whose frequency width does not exceed the fundamentalfrequency of said impulses by which there is yielded an output voltagewhose value is a function of the frequency relation existing betweensaid wave and the most proximate component in said spectrum. Y

2. A circuit-arrangement for producing an output voltage, whose value isa function of the frequency relation existing between an oscillatorywave and the most proximate component in the harmonic spectrum ofperiodic voltage impulses, comprising an electron discharge tubeprovided with a cathode, a grid and an anode, a gridcathode circuit forsaid tube, an anode-cathode circuit for said tube, a low-pass filterhaving its input connected in the anode-cathode circuit of said tube,means to apply an oscillatory Wave to the grid-cathode circuit of saidtube, and means to apply periodic positive voltage impulses having apredetermined repetition rate to said anode-cathode circuit to rendersaid tube conductive solely during the occurrence of said im pulses,said impulses having a duration which is short relative to the intervalbetween successive impulses, said filter having a band-passcharacteristic whose frequency width does not exceed approximately halfthe rate of said impulses whereby said filter yields an output voltagewhose value is a function of the frequency relation existing betweensaid wave and the most proximate component in said spectrum.

3. A circuit-arrangement for producing an output voltage, whose value isa function of the frequency relation existing between an oscillatoryWave and the most proximate component in the harmonic spectrum ofperiodic voltage impulses, comprising an electron discharge tubeprovided with a cathode, a grid and an anode, a gridcathode circuit forsaid tube, an anode-cathode circuit for said tube, a low-pass filterhaving its input connected in theanode-cathode circuit of said tube,means to apply an oscillatory wave to the grid-cathode circuit of saidtube, means to apply a bias potential to said anode-cathode circuit tomaintain said tube normally non-conductive, and means to apply periodicvoltage impulses having a predetermined periodicity to saidanode-cathode circuit to render said tube conductive solely during theoccurrence of said impulses, said impulses having a width which is shortrelative to the interval between successive impulses, said filter havinga band-pass characteristic Whose frequency width is less thanapproximately half the periodicity of said impulses whereby said filteryields an output voltage whose value is a function of the frequencyrelation existing between said wave and the most proximate component insaid spectrum.

4. A circuit-arrangement for producing an output voltage, whose value isa function of a frequency relation existing between an oscillatory waveand the most proximate component in the harmonic spectrum of periodicvoltage impulses, comprising an electron discharge tube provided with acathode, a grid and an anode, an oscillatory wave source connectedbetween said grid and said cathode, a low-pass filter connected betweensaid anode and said cathode, a periodic voltage impulse sourceinterposed between said anode and said filter to render said tubeconductive solely during the occurrence of said impulses, said impulsesource producing impulses at a predetermined rate and having a durationwhich is short relative to the interval between successive impulses,said filter having a band-pass characteristic whose frequency width issubstantially equal to one-half the rate of said impulses.

5. A circuit-arrangement for producing an output voltage, whose value isa function of a frequency relation existing between an oscillatory waveand the most proximate component in the harmonic spectrum of periodicvoltage impulses; comprising an electron discharge tube provided with acathode, a grid and an anode, an oscillatory wave source connectedbetween said grid and said cathode, a low-pass filter connected betweensaid anode and said cathode, a bias supply interposed between saidcathode and said filter to maintain said tube normally non-conductive, aperiodic voltage impulse source interposed between said anode and saidfilter to render said tube conductive solely during the occurrence ofsaid impulses, said impulse source producing impulses having apredetermined periodicity and a duration which is short relative to theinterval between successive impulses, said filter having a band-passcharacteristic whose frequency width is substantially equal to one-halfthe periodicity of said impulses.

JOHANNES MARIN'US LODEVICUS JANSSEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,564,627 Round Dec. 8, 19251,912,234 Willoughby May 30, 1933 2,173,164 Hansell Sept. 19, 19392,246,958 Strutt et al June 24, 1941 2,258,877 Barber Oct. 14, 19412,416,367 Young July 30, 1942 2,401,945 Linder June 11, 1946 2,408,821Stearns Oct. 3, 1946 2,408,858 Keiser Oct. 8, 1946 2,432,180 'I'ourshouDec. 9, 1947 2,445,584 Ramo July 20, 1948 2,504,636 Bradley Apr. 13,1950 OTHER REFERENCES Article by G. Grammer, Q. S. T., June 1938, pages21 and 24, 98 and 100,

